Radio reception apparatus, signal processing timing control method, and signal processing timing control program

ABSTRACT

In a radio reception apparatus, a variable gain of a reception amplifier is adjusted by an AGC control unit for each frame of a received signal for execution of an AGC operation. The AGC control unit determines and indicates to a digital signal processing unit an AGC operation end point of time. The digital signal processing unit executes prescribed signal processing on a digital signal obtained after the end of the AGC operation, in a known signal segment. Therefore, reception errors caused by erroneous amplitude values of digital signals resulting from the AGC operation can be prevented.

TECHNICAL FIELD

The present invention relates to a radio reception apparatus, a signalprocessing timing control method, and a signal processing timing controlprogram, and more particularly to a radio reception apparatus, a signalprocessing timing control method, and a signal processing timing controlprogram for use, for example, in a base station in a mobilecommunication system requiring a high communication quality as in datacommunication.

BACKGROUND ART

Conventionally, Automatic Gain Control (AGC) has widely been employed inorder to converge a level of a received signal at a desired level in aradio reception apparatus. FIG. 5 is a schematic block diagram showing,as an exemplary conventional radio reception apparatus employing AGC, aconfiguration of a radio reception apparatus for use in a mobilecommunication system (a base station or mobile station thereof), forexample, PHS (Personal Handyphone System).

Referring to FIG. 5, a burst signal in each frame of PHS received at anantenna 1 is amplified by a reception amplifier 2 with a variable gain.At the start of reception of a burst signal of each frame, the gain ofreception amplifier 2 is preset at a certain initial value.

The received signal amplified by reception amplifier 2 is converted intoa digital signal by an A/D converter 3 and is then subjected toquadrature modulation in a prescribed modulation method (for example,π/4QPSK (Quadrature Phase Shift Keying) method) by a quadraturemodulator 4.

The output of quadrature modulator 4 is provided to a digital signalprocessing unit 5 for prescribed signal processing (for example, asynchronization process, propagation path estimation, weight estimationfor adaptive arrays, and the like) and is also provided to an AGCcontrol unit 6.

AGC control unit 6 monitors a digital output supplied from quadraturemodulator 4, generates a control output for adjusting a variable gain ofreception amplifier 2 such that a power level of the analog receivedsignal in the frame converges at a prescribed level, and provides thecontrol output to a gain control input of reception amplifier 2.

In this manner, in the conventional AGC operation, a burst signal ineach frame of a received signal is received while its reception powerlevel information is measured for use in adjusting the gain of thereception amplifier. For each frame, it usually takes approximately afew μ seconds from the starting point of time of each frame to convergean analog received signal level at a prescribed level through theabove-described AGC operation.

Therefore, a few leading symbols of a digital signal for each frameobtained by performing A/D conversion on the output from receptionamplifier 2 using A/D converter 3 during such a time period of about afew μ seconds may suffer erroneous amplitude values.

FIG. 6 is a diagram showing a waveform of a digital signal in a frameobtained through the above-described AGC operation. In FIG. 6, the axisof abscissas shows time (the number of symbols in the frame) and theaxis of ordinates shows the magnitude (amplitude value) of the digitalsignal subjected to the AGC process.

As can be seen from the waveform diagram of FIG. 6, for example, if aninitial value of a gain of reception amplifier 2 is set at a properlylarge value, a digital signal obtained in the beginning of the frame hasa swell in its amplitude value and it takes a period of a few symbols toconverge the amplitude value at a proper amplitude value through the AGCprocess. It is noted that it is actually impossible to set anappropriate initial value as an initial gain of reception amplifier 2since the degree of fading varies greatly depending on a propagationpath.

In a signal format of PHS, for example, a head portion of each frameincludes a known signal segment including a preamble (PR), a unique word(UW), and the like. A known signal in this segment is used to perform avariety of signal processing as described above.

In the example shown in FIG. 6, a digital signal having an erroneousamplitude value occurs in a part of this known signal segment. Such asignal, however, is included as it is in the conventional digital signalprocessing segment. In other words, in the conventional mobilecommunication system such as PHS, since the well-known π/4QPSK method,for example, is generally employed as a modulation method, no receptionerror takes place during signal processing even if the amplitude valueof the digital signal resulting from AGC is erroneous as describedabove.

More specifically, in the π/4QPSK method, a symbol point of a receivedsignal corresponds to any of eight signal points positionedconcentrically on an IQ coordinate plane, as is well known. Therefore,there is a one-to-one correspondence between a phase angle (direction)on the IQ coordinate plane and the symbol point. In other words, in thismethod, since a determination is made only based on a phase component ofa digital signal, a symbol point is correctly recognized even if theamplitude value of the digital signal is inappropriate. Therefore, areception error does not take place in signal processing at a subsequentstage.

Recent mobile communication systems, however, require data transmissionof larger volume at higher speed, as compared with conventional voicecommunication. Accordingly, multi-value modulation methods having numberof multi-values larger than the π/4QPSK method mentioned above have beendeveloped. As an example of such multi-value modulation method, thewell-known 16QAM (Quadrature Amplitude Modulation) method has beenpractically utilized in some type of data communication. According tothe 16QAM modulation method, a symbol point of a received signalcorresponds to any of a total of 16 signal points on the coordinateplane, arranged four by four in a lattice form in each quadrant of theIQ coordinate plane, as is well known. In other words, in this method, adetermination of a symbol point is made based on both of a phasecomponent and an amplitude component of a digital signal.

When the 16 QAM method is employed as a modulation method for PHS and ifthe amplitude value of the digital signal is inappropriate as shown inFIG. 6, a certain symbol point may possibly be recognized erroneously asanother symbol point with the same phase with a different amplitudevalue, resulting in a reception error in signal processing at asubsequent stage.

The 16QAM method has already been put into practical use in some typesof data communication. In a data format in such data communication, asufficiently long signal segment is provided as a known signal segmentsuch as a preamble. Even if the amplitude value takes an erroneous valueresulting from AGC in a head portion of data, by ignoring the signalsegment suffering this erroneous amplitude value, required signalprocessing can be performed sufficiently in the remaining known signalsegment.

In the mobile communication system such as PHS, however, the knownsignal segment such as PR, UW is limited to a short segment of a fewsymbols at the head of each frame according to a signal format standardin order to secure transmission data volume. Therefore, when amulti-value modulation method such as the 16QAM method is employed, theamplitude value is erroneous in a large segment within the known signalsegment, as shown in FIG. 6, resulting in a reception error during thedigital signal processing.

An object of the present invention is therefore to provide a radioreception apparatus, a signal processing timing control method, and asignal processing timing control program, in which reception errorsresulting from a AGC process are prevented even when a multi-valuemodulation method is employed to allow for high quality and large volumetransmission, in a mobile communication system having a signal formatthat does not allow for a sufficient length of a known signal segment.

DISCLOSURE OF THE INVENTION

In accordance with one aspect of the present invention, a radioreception apparatus processing a received signal formed of a signalseries having a known signal segment at a head portion includesamplification means, signal processing means, gain control means, anddetermination means. The amplification means amplifies the receivedsignal with a variable gain. The signal processing means performsprescribed signal processing on the received signal amplified by theamplification means. The gain control means controls the variable gainof the amplification means such that a level of the received signalamplified by the amplification means converges at a prescribed level.The determination means determines and indicates to the signalprocessing means a signal segment length to be excluded from theprescribed signal processing from a head of the received signal so as toavoid an effect of control of the variable gain. The signal processingmeans performs the prescribed signal processing on a signal segment,excluding the indicated signal segment length, from the head of thereceived signal.

In accordance with another aspect of the present invention, a radioreception apparatus processing a received signal formed of a signalseries having a known signal segment at a head portion includesamplification means, signal processing means, and control means. Theamplification means amplifies the received signal with a variable gain.The signal processing means performs prescribed signal processing on thereceived signal amplified by the amplification means. The control meanscontrols the variable gain of the amplification means such that a levelof the received signal amplified by the amplification means converges ata prescribed level, and determines and indicates to the signalprocessing means a signal segment length from a head of the receivedsignal that is required for the level of the received signal to convergeat the prescribed level. The signal processing means performs theprescribed signal processing on a signal segment, excluding theindicated signal segment length, from the head of the received signal.

In accordance with a further aspect of the present invention, a radioreception apparatus processing a received signal formed of a signalseries having a known signal segment at a head portion includesamplification means, signal processing means, and control means. Theamplification means amplifies the received signal with a variable gain.The signal processing means performs prescribed signal processing on thereceived signal amplified by the amplification means. The control meanscontrols the variable gain of the amplification means such that a levelof the received signal amplified by the amplification means converges ata prescribed level, and determines and indicates to the signalprocessing means passage of a prescribed signal segment length from ahead of the received signal that is set within the known signal segment.The signal processing mean is responsive to the indication of thepassage for performing the prescribed signal processing on a signalsegment excluding the prescribed signal segment length from the head ofthe received signal.

Preferably, the control means does not control the variable gain, whenthe level of the received signal amplified by the amplification meansinitially converges at the prescribed level, and the signal processingmeans performs the prescribed signal processing from the head of thereceived signal.

In accordance with yet another aspect of the present invention, a radioreception apparatus processing a received signal formed of a signalseries having a known signal segment at a head portion includesamplification means, digital modulation means, and digital signalprocessing means. The amplification means amplifies the received signalwith a variable gain. The digital modulation means modulates thereceived signal amplified by the amplification means into a digitalreceived signal. The digital signal processing means receives thedigital received signal, controls the variable gain of the amplificationmeans such that a level of the received signal amplified by theamplification means converges at a prescribed level, determines a signalsegment length to be excluded from prescribed signal processing from ahead of the received signal so as to avoid an effect of control of thevariable gain, and performs the prescribed signal processing on a signalsegment, excluding the determined signal segment length, from the headof the received signal.

In accordance with still another aspect of the present invention, aradio reception apparatus processing a received signal formed of asignal series having a known signal segment at a head portion includesamplification means, digital modulation means, and digital signalprocessing means. The amplification means amplifies the received signalwith a variable gain. The digital modulation means modulates thereceived signal amplified by the amplification means into a digitalreceived signal. The digital signal processing means receives thedigital received signal, controls the variable gain of the amplificationmeans such that a level of the received signal amplified by theamplification means converges at a prescribed level, determines a signalsegment length from a head of the received signal that is required forthe level of the received signal to converge at the prescribed level,and performs prescribed signal processing on a signal segment, excludingthe determined signal segment length, from the head of the receivedsignal.

In accordance with a still further aspect of the present invention, aradio reception apparatus processing a received signal formed of asignal series having a known signal segment at a head portion includesamplification means, digital modulation means, and digital signalprocessing means. The amplification means amplifies the received signalwith a variable gain. The digital modulation means modulates thereceived signal amplified by the amplification means into a digitalreceived signal. The digital signal processing means receives thedigital received signal, controls the variable gain of the amplificationmeans such that a level of the received signal amplified by theamplification means converges at a prescribed level, determines passageof a prescribed signal segment length from a head of the received signalthat is set within the known signal segment, and, in response to thedetermination, performs prescribed signal processing on a signal segmentexcluding the prescribed signal segment length from the head of thereceived signal.

Preferably, when the level of the received signal amplified by theamplification means initially converges at the prescribed level, thedigital signal processing means does not control the variable gain andperforms the prescribed signal processing from the head of the receivedsignal.

In accordance with another aspect of the present invention, a signalprocessing timing control method in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control methodincludes the steps of: controlling the variable gain of theamplification means such that a level of the received signal amplifiedby the amplification means converges at a prescribed level; determininga signal segment length to be excluded from prescribed signal processingfrom a head of the received signal so as to avoid an effect of controlof the variable gain; and performing the prescribed signal processing ona signal segment, excluding the determined signal segment length, fromthe head of the received signal.

In accordance with a further aspect of the present invention, a signalprocessing timing control method in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control methodincludes the steps of: controlling the variable gain of theamplification means such that a level of the received signal amplifiedby the amplification means converges at a prescribed level; determininga signal segment length from a head of the received signal that isrequired for the level of the received signal to converge at theprescribed level; and performing prescribed signal processing on asignal segment, excluding the determined signal segment length, from thehead of the received signal.

In accordance with still another aspect of the present invention, asignal processing timing control method in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control methodincludes the steps of: controlling the variable gain of theamplification means such that a level of the received signal amplifiedby the amplification means converges at a prescribed level; determiningpassage of a prescribed signal segment length from a head of thereceived signal that is set within the known signal segment; and, inresponse to the determination, performing prescribed signal processingon a signal segment excluding the prescribed signal segment length fromthe head of the received signal.

Preferably, the signal processing timing control method further includesthe steps of: determining whether the level of the received signalamplified by the amplification means initially converges at theprescribed level; and performing the prescribed signal processing fromthe head of the received signal without controlling the variable gain,when it is determined that the level of the received signal amplified bythe amplification means initially converges at the prescribed level.

In accordance with a still further aspect of the present invention, asignal processing timing control program in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control programcauses a computer to execute the steps of: controlling the variable gainof the amplification means such that a level of the received signalamplified by the amplification means converges at a prescribed level;determining a signal segment length to be excluded from prescribedsignal processing from a head of the received signal so as to avoid aneffect of control of the variable gain; and performing the prescribedsignal processing on a signal segment, excluding the determined signalsegment length, from the head of the received signal.

In accordance with yet another aspect of the present invention, a signalprocessing timing control program in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control programcauses a computer to execute the steps of: controlling the variable gainof the amplification means such that a level of the received signalamplified by the amplification means converges at a prescribed level;determining a signal segment length from a head of the received signalthat is required for the level of the received signal to converge at theprescribed level; and performing prescribed signal processing on asignal segment, excluding the determined signal segment length, from thehead of the received signal.

In accordance with yet still another aspect of the present invention, asignal processing timing control program in a radio reception apparatusprocessing a received signal formed of a signal series having a knownsignal segment at a head portion is provided. The radio receptionapparatus includes amplification means amplifying the received signalwith a variable gain. The signal processing timing control programcauses a computer to execute the steps of: controlling the variable gainof the amplification means such that a level of the received signalamplified by the amplification means converges at a prescribed level;determining passage of a prescribed signal segment length from a head ofthe received signal that is set within the known signal segment; and, inresponse to the determination, performing prescribed signal processingon a signal segment excluding the prescribed signal segment length fromthe head of the received signal.

Preferably, the signal processing timing control program further causesa computer to execute the steps of determining whether the level of thereceived signal amplified by the amplification means initially convergesat the prescribed level; and performing the prescribed signal processingfrom the head of the received signal without controlling the variablegain, when it is determined that the level of the received signalamplified by the amplification means initially converges at theprescribed level.

Therefore, in accordance with the present invention, even when amulti-value modulation method is employed in a mobile communicationsystem having a signal format that does not allow for a sufficientlength of a known signal segment, signal processing is performed in aknown signal segment excluding a segment affected by an AGC process.Accordingly, reception errors resulting from the AGC process can beprevented.

Furthermore, in accordance with the present invention, even when amulti-value modulation method is employed in a mobile communicationsystem having a signal format that does not allow for a sufficientlength of a known signal segment, a time point when an AGC process endsis determined, so that signal processing is performed in a known signalsegment excluding the AGC process period of time. Accordingly, receptionerrors resulting from the AGC process can be prevented.

In addition, in accordance with the present invention, even when amulti-value modulation method is employed in a mobile communicationsystem having a signal format that does not allow for a sufficientlength of a known signal segment, a minimum segment required for signalprocessing in the latter half of a known signal segment is determined bycounting, so that the signal processing is performed in that segment.Accordingly, reception errors resulting from the AGC process can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram showing a configuration of a radioreception apparatus in an embodiment of the present invention.

FIG. 2 is a timing diagram illustrating an operational timing of theradio reception apparatus shown in FIG. 1.

FIG. 3 is a flowchart illustrating an exemplary operation of the radioreception apparatus shown in FIG. 1.

FIG. 4 is a flowchart illustrating another exemplary operation of theradio reception apparatus shown in FIG. 1.

FIG. 5 is a block diagram showing a configuration of a conventionalradio reception apparatus.

FIG. 6 is a timing diagram illustrating an operational timing of theradio reception apparatus shown in FIG. 5.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, an embodiment of the present invention will bedescribed in detail with reference to the figures. It is noted that inthe figures the same or corresponding parts will be denoted with thesame reference characters and the description thereof will not berepeated.

FIG. 1 is a functional block diagram showing a configuration of a radioreception apparatus applied in a base station of a mobile communicationsystem, for example, PHS, in accordance with the embodiment of thepresent invention. It is assumed that the embodiment described belowemploys the well-known 16QAM as a multi-value modulation method.

The radio reception apparatus shown in FIG. 1 is the same as theconventional radio reception apparatus shown in FIG. 5 except thefollowing: in addition to the operation of producing an AGC controlsignal in the AGC control unit shown in FIG. 5, an AGC control unit 16generates a signal indicative of passage of a segment that should beexcluded from signal processing in a head portion of a known signalsegment for each frame and provides the signal to a digital signalprocessing unit 15.

Digital signal processing unit 15 performs signal processing similar tothat in digital signal processing unit 5 in FIG. 5 (a synchronizationprocess, a propagation path estimation process, an adaptive array weightestimation process, and the like) on a known signal segment, excludingthe segment indicated by the signal from AGC control unit 16, of theknown signal segment of each frame.

FIG. 2 is a waveform diagram illustrating an operation of the radioreception apparatus shown in FIG. 1. In the waveform diagram of theconventional example shown in FIG. 6, signal processing is performedfrom the head of the known signal segment of each frame, irrespective ofthe swell in the amplitude value of the digital signal due to the AGCprocess, whereas, in the embodiment of the present invention shown inFIG. 2, signal processing is performed after the swell of the digitalsignal due to the AGC process converges and then the effect of the AGCprocess disappears.

In this way, when the AGC operation ends within the known signal segmentsuch as PR, UW in PHS, by ignoring the AGC period of a few symbolshaving erroneous amplitude values, prescribed signal processing (asynchronization process, propagation path estimation, adaptive arrayweight estimation, and the like) is performed in the remaining knownsignal segment. Accordingly, reception errors in the digital signalprocessing unit can be prevented thereby improving the communicationquality.

In this way, the method of determining a known signal segment foravoiding effects of the AGC process may include the followings, forexample.

According to a first method, an AGC control unit 16 of FIG. 1 determineswhether a reception level converges at a prescribed level, that is,whether the AGC process ends and a digital signal having a properamplitude value begins to be obtained, and notifies digital signalprocessing unit 15 of the determined time point. Immediately when it isdetermined that a digital signal having a proper amplitude value beginsto be obtained, prescribed signal processing on a digital signal isstarted in digital signal processing unit 15.

Therefore, in a limited length of a known signal segment, a time pointwhen a signal suitable for signal processing is obtained can bedetermined as quickly as possible, so that prescribed signal processingcan be performed with maximum efficiency without reception errors in theremaining known signal segment.

According to a second method, a prescribed number of unnecessary symbols(a signal segment length) is counted from the head of the known signalsegment, such that a prescribed minimum number of symbols (a signalsegment length) required for signal processing in digital signalprocessing unit 15 are spared in the latter half of the known signalsegment. Digital signal processing unit 15 is notified of the time pointwhen the number of unnecessary symbols have passed. Irrespective of theresult of the AGC process, digital signal processing unit 15 startsprescribed signal processing on a digital signal at the time when aprescribed number of symbols have passed.

Accordingly, the minimum known signal segment required for theprescribed processing can be utilized entirely, even in the segment inwhich the effect of the AGC process remains more or less.

The function of AGC control unit 16 and digital signal processing unit15 shown in FIG. 1 can be implemented by software, for example, using aDigital Signal Processor (DSP) or the like. A method according to theembodiment of the present invention is executed by software according toeach flowchart using this DSP. This DSP reads a program including eachstep of each flowchart from a not-shown memory for execution. Thisprogram can be installed from the outside source.

FIG. 3 is a flowchart showing a control where the first method describedabove is implemented by software.

First, at step S1, an initial value of a gain for an AGC process ofreception amplifier 2 in the frame is set, and a count value of thenumber of symbols to be invalidated is set at zero.

Then, at step S2, measurement of a reception signal level in the frame(the magnitude of the digital signal subjected to A/D conversion) isstarted.

At step S3, if the setting of the initial value is appropriate, andtherefore the reception level at the start of reception does not largelydeviate from a prescribed level and substantially converges, it can beassumed that the reception errors as described above will not takeplace. Therefore, the AGC operation is not started, and the above-notedinitial value is set as it is for reception amplifier 2 (step S4). Then,prescribed digital signal processing is performed from a normal signalprocessing segment, that is, the head of the known signal segment (stepS5). Thereafter, all the processes are ended at step S11.

On the other hand, if it is determined at step S3 that the initialreception level largely deviates from the prescribed level, an AGCoperation is started.

First, at step S6, the gain of reception amplifier 2 is adjusted. Atstep S7, the level of the received signal (the magnitude of the digitalsignal) is measured again. As a result, until it is determined at stepS8 that the reception level converges at the prescribed level, theprocesses at steps S6–8 are repeated. If it is determined that thereception level converges, the AGC operation is ended at step S8, and atstep S9, the number of symbols to be invalidated that are required forthe AGC process is calculated.

Then, at step S10, prescribed digital signal processing is performed onthe remaining known signal segment obtained by eliminating the invalidsymbols from the head of the known-signal segment. All the processes areended at step S11.

In the example shown in FIG. 3, in the limited length of the knownsignal segment, the time point when a signal suitable for signalprocessing is obtained, that is, the AGC ending point of time, isdetermined as quickly as possible, so that the prescribed signalprocessing can be performed without reception errors with the maximumefficiency in the remaining known signal segment.

FIG. 4 is a flowchart showing a control where the second methoddescribed above is implemented by software.

First, at step S31, an initial value of a gain for an AGC process ofreception amplifier 2 in the frame is set, and the number of symbols tobe invalidated is set at a predetermined value N. Furthermore, a counterAGC_cnt, which counts an AGC process time corresponding to theprescribed number N of invalid symbols, is set at zero.

Then, at step S32, measurement of the reception signal level (themagnitude of the digital signal subjected to A/D conversion) in theframe is started.

At step S33, if the setting of the initial value is appropriate, andtherefore the reception level at the start of reception does not largelydeviate from a prescribed level and substantially converges, it can beassumed that the reception errors described above will not take place.Accordingly, the AGC operation is not started, and the initial valueabove is set as it is for reception amplifier 2 (step S34). Theprescribed signal processing is performed from a normal signalprocessing segment, that is, the head of the known signal segment (stepS35). Then, all the processes are ended at step S42.

On the other hand, if it is determined at step S33 that the initialreception level largely deviates from the prescribed level, the AGCoperation is started.

First, at step S36, the gain of reception amplifier 2 is adjusted. Atstep S37, the level of the received signal (the magnitude of the digitalsignal) is measured again. As a result, at step S38, until it isdetermined that the reception level converges at the prescribed level oruntil it is determined that the count of counter AGC_cnt reaches a limitvalue corresponding to the number N of invalid symbols, the processes atsteps S36–38 are repeated while AGC_cnt is incremented one by one, atstep S39.

If it is determined at step S38 that the reception level converges (theAGC operation ends) or that AGC_cnt reaches the limit value, theprescribed number N of invalid symbols is read at step S40.

Then, at step S41, irrespective of whether the AGC operation ends, theprescribed digital signal processing is performed on the remaining knownsignal segment obtained by eliminating the above-mentioned prescribednumber N of invalid symbols from the head of the known signal segment.At step S42, all the processes are ended.

In the example shown in FIG. 4, the minimum known signal segment (thesegment excluding N) required for the prescribed processing can beutilized entirely, even in the segment in which the effect of the AGCprocess remains more or less.

Usually, it is effective to estimate the gain initial value of receptionamplifier 2 in each frame from the magnitude of the reception levelbefore the previous frame. However, when the reception level variesgreatly due to the fading environment and the like, the aforementionedreception errors are likely to take place. Then, the method shown inFIG. 3 or 4 as described above is particularly effective.

Although the foregoing embodiment has been described as employing the16QAM method as a multi-value modulation method, the multi-valuemodulation method applicable to the present invention is not limited tothe 16QAM method and any modulation method is applicable as long as theamplitude information of the received signal is determined.

Although the foregoing embodiment has been described with respect to PHSas an exemplary mobile communication system, the present invention isnot limited to PHS and may be applied to a mobile communication systemhaving such a format in that the length of the known signal segment islimited.

As described above, in accordance with the present invention, receptionerrors in the digital signal processing unit resulting from the AGCprocess for the analog received signal can be prevented even if amulti-value modulation method such as 16QAM is employed to allow forhigh quality and large volume transmission, in a mobile communicationsystem such as PHS having a signal format in which the standard does notallow a sufficient length of the known signal segment.

INDUSTRIAL APPLICABILITY

As described above, the radio reception apparatus, the signal processingtiming control method, and the signal processing timing control programin accordance with the present invention are useful in a mobilecommunication system employing a multi-value modulation method, sincereception errors resulting from an AGC process can be prevented even ina signal format that does not allow for a sufficient length of a knownsignal segment.

1. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising: amplification means amplifying said received signal with a variable gain; signal processing means performing prescribed signal processing on said received signal amplified by said amplification means; gain control means controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; and determination means determining and indicating to said signal processing means a signal segment length to be excluded from said prescribed signal processing from a head of said received signal so as to avoid an effect of control of said variable gain, wherein said signal processing means performs said prescribed signal processing on a signal segment, excluding said indicated signal segment length, from the head of said received signal.
 2. The radio reception apparatus according to claim 1, wherein said control means does not control said variable gain, when the level of said received signal amplified by said amplification means initially converges at said prescribed level, and said signal processing means performs said prescribed signal processing from the head of said received signal.
 3. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising; amplification means amplifying said received signal with a variable gain; signal processing means performing prescribed signal processing on said received signal amplified by said amplification means; and control means controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level, and determining and indicating to said signal processing means a signal segment length from a head of said received signal that is required for the level of said received signal to converge at said prescribed level, wherein said signal processing means performs said prescribed signal processing on a signal segment, excluding said indicated signal segment length, from the head of said received signal.
 4. The radio reception apparatus according to claim 3, wherein said control means does not control said variable gain, when the level of said received signal amplified by said amplification means initially converges at said prescribed level, and said signal processing means performs said prescribed signal processing from the head of said received signal.
 5. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising: amplification means amplifying said received signal with a variable gain; signal processing means performing prescribed signal processing on said received signal amplified by said amplification means; control means controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level, and determining and indicating to said signal processing means passage of a prescribed signal segment length from a head of said received signal that is set within said known signal segment, wherein said signal processing mean is responsive to the indication of said passage for performing said prescribed signal processing on a signal segment excluding said prescribed signal segment length from the head of said received signal.
 6. The radio reception apparatus according to claim 5, wherein said control means does not control said variable gain, when the level of said received signal amplified by said amplification means initially converges at said prescribed level, and said signal processing means performs said prescribed signal processing from the head of said received signal.
 7. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising: amplification means amplifying said received signal with a variable gain; digital modulation means modulating said received signal amplified by said amplification means into a digital received signal; and digital signal processing means receiving said digital received signal, wherein said digital signal processing means controls said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level, determines a signal segment length to be excluded from prescribed signal processing from a head of said received signal so as to avoid an effect of control of said variable gain, and performs said prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 8. The radio reception apparatus according to claim 7, wherein when the level of said received signal amplified by said amplification means initially converges at said prescribed level, said digital signal processing means does not control said variable gain and performs said prescribed signal processing from the head of said received signal.
 9. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising: amplification means amplifying said received signal with a variable gain; digital modulation means modulating said received signal amplified by said amplification means into a digital received signal; and digital signal processing means receiving said digital received signal, wherein said digital signal processing means controls said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level, determines a signal segment length from a head of said received signal that is required for the level of said received signal to converge at said prescribed level, and performs prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 10. The radio reception apparatus according to claim 9, wherein when the level of said received signal amplified by said amplification means initially converges at said prescribed level, said digital signal processing means does not control said variable gain and performs said prescribed signal processing from the head of said received signal.
 11. A radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, comprising: amplification means amplifying said received signal with a variable gain; digital modulation means modulating said received signal amplified by said amplification means into a digital received signal; and digital signal processing means receiving said digital received signal, wherein said digital signal processing means controls said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level, determines passage of a prescribed signal segment length from a head of said received signal that is set within said known signal segment, and in response to said determination, performs prescribed signal processing on a signal segment excluding said prescribed signal segment length from the head of said received signal.
 12. The radio reception apparatus according to claim 11, wherein when the level of said received signal amplified by said amplification means initially converges at said prescribed level, said digital signal processing means does not control said variable gain and performs said prescribed signal processing from the head of said received signal.
 13. A signal processing timing control method in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control method comprising the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining a signal segment length to be excluded from prescribed signal processing from a head of said received signal so as to avoid an effect of control of said variable gain; and performing said prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 14. The signal processing timing control method according to claim 13, further comprising the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level.
 15. A signal processing timing control method in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control method comprising the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining a signal segment length from a head of said received signal that is required for the level of said received signal to converge at said prescribed level; and performing prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 16. The signal processing timing control method according to claim 15, further comprising the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level.
 17. A signal processing timing control method in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control method comprising the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining passage of a prescribed signal segment length from a head of said received signal that is set within said known signal segment; and in response to said determination, performing prescribed signal processing on a signal segment excluding said prescribed signal segment length from the head of said received signal.
 18. The signal processing timing control method according to claim 17, further comprising the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level.
 19. A signal processing timing control program in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control program causing a computer to execute the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining a signal segment length to be excluded from prescribed signal processing from a head of said received signal so as to avoid an effect of control of said variable gain; and performing said prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 20. The signal processing timing control program according to claim 19, further causing a computer to execute the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level.
 21. A signal processing timing control program in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control program causing a computer to execute the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining a signal segment length from a head of said received signal that is required for the level of said received signal to converge at said prescribed level; and performing prescribed signal processing on a signal segment, excluding said determined signal segment length, from the head of said received signal.
 22. The signal processing timing control program according to claim 21, further causing a computer to execute the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level.
 23. A signal processing timing control program in a radio reception apparatus processing a received signal formed of a signal series having a known signal segment at a head portion, said radio reception apparatus including amplification means amplifying said received signal with a variable gain, said signal processing timing control program causing a computer to execute the steps of: controlling said variable gain of said amplification means such that a level of said received signal amplified by said amplification means converges at a prescribed level; determining passage of a prescribed signal segment length from a head of said received signal that is set within said known signal segment; and in response to said determination, performing prescribed signal processing on a signal segment excluding said prescribed signal segment length from the head of said received signal.
 24. The signal processing timing control program according to claim 23, further causing a computer to execute the steps of: determining whether the level of said received signal amplified by said amplification means initially converges at said prescribed level; and performing said prescribed signal processing from the head of said received signal without controlling said variable gain, when it is determined that the level of said received signal amplified by said amplification means initially converges at said prescribed level. 